1. Field of the Invention
The present invention relates to a wireless sensor network and, in particular, to a communication terminal and method for a wireless sensor network in which a plurality of terminals contend to transmit packets through a shared single channel in an active period.
2. Description of the Related Art
A wireless sensor network can be implemented in the form of Wireless Local Area Network (WLAN) and Wireless Personal Area Network (WPAN) technologies in consideration of sensing area coverage. Typically, a WLAN is implemented on the basis of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard which specifies wireless access network having a range up to 100 m. Meanwhile, a WPAN may also be implemented using the IEEE 802.16 based technologies, e.g., Bluetooth, ZigBee, and Ultra Wideband (UWB). A wireless sensor network is composed of a plurality of terminals that share a single communication channel and transmit data during active periods. That is, each terminal collects data in real time and sends the collected data in the form of a packet during an active period.
In the conventional wireless sensor network, each sensor node attempts to transmit the packet during a contention window defined in the active period. If the channel assessed is available, then the sensor node transmits the packet. However, if the channel assessed is unavailable or fails to transmit the packet, the sensor node resets the contention window, which is elongated in exponential manner, and retries to transmit the packet. Accordingly, as the number of reattempts of the packet transmission increases, the contention window expands exponentially, resulting in degradation of channel utilization efficiency.